Hitherto, there have been techniques for capturing an image of a person, detecting a face from a captured person's image, obtaining a face image feature amount of a face image from a face region, obtaining a similarity by collating the obtained face image feature amount with a face image feature amount registered in a collation list, and comparing the obtained similarity with a preliminarily set threshold value to thereby determine whether the person of which the image is captured is identical to a person registered in the collation list (see, e.g., Patent Documents 1 and 2).
FIG. 26 is a schematic diagram illustrating a configuration of a conventional collating device. As illustrated in this figure, the face of a person is detected from an image obtained as a result of image capture of the person by a camera. A face image feature amount is extracted from a face region of the detected face. A similarity is obtained by comparing the extracted face image feature amount with a face image feature amount registered in the collation list. Then, alarm determination is performed, based on the obtained similarity. If the similarity is equal to or more than a threshold value, alarm notification is performed. According to this figure, the threshold value is set at “50”. The similarity between a person 500 whose face is detected and a person 501 registered in a collation list is “55”. The similarity between another person 502 whose face is detected and the person 501 is “30”. Thus, alarm notification is performed corresponding to the person 501 whose similarity exceeds the threshold value “50”.